U.S. patent application number 13/603440 was filed with the patent office on 2014-01-30 for auto-focus method.
This patent application is currently assigned to ALTEK CORPORATION. The applicant listed for this patent is Ming-Jiun Liaw, Chien-Hsiang Lin. Invention is credited to Ming-Jiun Liaw, Chien-Hsiang Lin.
Application Number | 20140029929 13/603440 |
Document ID | / |
Family ID | 49994984 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140029929 |
Kind Code |
A1 |
Lin; Chien-Hsiang ; et
al. |
January 30, 2014 |
AUTO-FOCUS METHOD
Abstract
An auto-focus (AF) method adapted for an image capturing device
includes following steps. When a first press signal generated by a
user pressing a button of the image capturing device is detected, a
local peak searching method is applied to perform an AF procedure.
It is determined whether a second press signal generated by the
user pressing the button is detected. If not, it is determined
whether a first released signal generated by the user releasing the
button is detected. The continuous pressing count is calculated
according to the first released signal and the first press signal
that are continuously generated. Whether the continuous pressing
count is greater than a first threshold is determined. If yes, a
global peak searching method is applied to perform the AF
procedure. If not, the local peak searching method is still applied
to perform the AF procedure.
Inventors: |
Lin; Chien-Hsiang; (Taoyuan
County, TW) ; Liaw; Ming-Jiun; (Miaoli County,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lin; Chien-Hsiang
Liaw; Ming-Jiun |
Taoyuan County
Miaoli County |
|
TW
TW |
|
|
Assignee: |
ALTEK CORPORATION
Hsinchu City
TW
|
Family ID: |
49994984 |
Appl. No.: |
13/603440 |
Filed: |
September 5, 2012 |
Current U.S.
Class: |
396/121 |
Current CPC
Class: |
H04N 5/23293 20130101;
G03B 13/36 20130101; H04N 5/232945 20180801; G02B 7/365 20130101;
H04N 5/23212 20130101; H04N 5/232123 20180801 |
Class at
Publication: |
396/121 |
International
Class: |
G03B 13/36 20060101
G03B013/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 26, 2012 |
TW |
101127066 |
Claims
1. An auto-focus method adapted for an image capturing device, the
auto-focus method comprising: determining whether a first press
signal generated by a user pressing a button of the image capturing
device is detected; if the first press signal is detected, applying
a local peak searching method to perform an auto-focus procedure;
determining whether a second press signal generated by the user
pressing the button is detected; if the second press signal is not
detected, determining whether a first released signal generated by
the user releasing the button is detected and calculating a
continuous pressing count according to the first released signal
and the first press signal that are continuously generated, wherein
the continuous pressing count is effected by the user continuously
pressing and releasing the button; and determining whether the
continuous pressing count is greater than a first threshold; if the
continuous pressing count is greater than the first threshold,
applying a global peak searching method to perform the auto-focus
procedure; if the continuous pressing count is not greater than the
first threshold, applying the local peak searching method to
perform the auto-focus procedure.
2. The auto-focus method as recited in claim 1, wherein if the
second press signal is not detected, the step of calculating the
continuous pressing count comprises: after detecting the first
released signal, determining whether another first press signal is
detected within a predetermined time period; if the another first
press signal is detected, up counting the continuous pressing
count; and if the another first press signal is not detected,
configuring an initial value of the continuous pressing count to be
0.
3. The auto-focus method as recited in claim 1, further comprising:
if the continuous pressing count is not greater than the first
threshold, applying the local peak searching method to perform the
auto-focus procedure and continuously detecting the second press
signal.
4. The auto-focus method as recited in claim 1, wherein the first
press signal is generated by the user pressing the button of the
image capturing device to perform the auto-focus procedure, and the
second press signal is generated by the user pressing the button of
the image capturing device to perform an exposure procedure.
5. The auto-focus method as recited in claim 4, wherein the first
press signal is generated by the user half-pressing the button, and
the second press signal is generated by the user completely
pressing the button.
6. An auto-focus method adapted for an image capturing device
having a zooming lens, the auto-focus method comprising:
determining whether a first press signal generated by a user
pressing a button of the image capturing device is detected; if the
first press signal is detected, applying a local peak searching
method to perform an auto-focus procedure and recording a first
lens-movement steps corresponding to the zooming lens when the
auto-focus procedure is successfully performed; determining whether
a second press signal generated by the user pressing the button is
detected; if the second press signal is not detected, determining
whether a first released signal generated by the user releasing the
button is detected and calculating the continuous pressing count
according to the first released signal and the first press signal
that are continuously generated, wherein the continuous pressing
count is effected by the user continuously pressing and releasing
the button; and determining whether the continuous pressing count
is greater than a first threshold; if the continuous pressing count
is greater than the first threshold, applying a global peak
searching method to perform the auto-focus procedure; if the
continuous pressing count is not greater than the first threshold,
applying the local peak searching method to perform the auto-focus
procedure and recording a second lens-movement steps corresponding
to the zooming lens when the auto-focus procedure is successfully
performed.
7. The auto-focus method as recited in claim 6, further comprising:
determining whether an absolute value of a difference between the
second lens-movement steps and the first lens-movement steps is
less than a step threshold; if the absolute value of the difference
between the second lens-movement steps and the first lens-movement
steps is less than the step threshold, up counting the step count;
and if the absolute value of the difference between the second
lens-movement steps and the first lens-movement steps is not less
than the step threshold, initializing the continuous pressing count
and the step count.
8. The auto-focus method as recited in claim 7, wherein the step of
determining whether the continuous pressing count is greater than
the first threshold further comprises: determining whether the step
count is greater than a second threshold; and if the continuous
pressing count is greater than the first threshold, and the step
count is greater than the second threshold, applying the global
peak searching method to perform the auto-focus procedure.
9. The auto-focus method as recited in claim 6, wherein if the
second press signal is not detected, the step of calculating the
continuous pressing count affected by the user continuously
pressing and releasing the button comprises: after detecting the
first released signal, determining whether another first press
signal is detected within a predetermined time period; if the
another first press signal is detected, up counting the continuous
pressing count; and if the another first press signal is not
detected, initializing the continuous pressing count and the step
count.
10. The auto-focus method as recited in claim 6, further
comprising: if the second press signal generated by the user
pressing the button is detected, shooting an image based on a
result of the auto-focus procedure.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Taiwan
application serial no. 101127066, filed on Jul. 26, 2012. The
entirety of the above-mentioned patent application is hereby
incorporated by reference herein and made a part of this
specification.
BACKGROUND OF THE DISCLOSURE
[0002] 1. Field of Invention
[0003] The invention relates to an auto-focus (AF) method, and more
particularly, to an AF method to automatically switch between
different focus value searching algorithms.
[0004] 2. Background of the Invention
[0005] Digital single lens reflex cameras (also named DSLR) are
characterized by delicate and complicated mechanical structures as
well as enhanced functionality and maneuverability. In addition to
shooting skills of users and environmental factors, the built-in
auto-focus (AF) systems of the DSLR also pose a significant impact
on the quality of photos.
[0006] Generally, according to the AF technology, the lens of the
DSLR is moved to adjust the relative distance between the lens and
an object to be shot. In response to different locations of the
lens, focus evaluation values (hereinafter "the focus values") of a
subject frame having the to-be-shot object may be respectively
calculated until the peak focus value is acquired. The peak focus
value represents the location of the lens where the subject frame
may have the optimal sharpness. Nonetheless, in order to obtain the
optimal sharpness, the lens is required to move back and forth, and
relevant calculations are continuously made. This thus leads to
significant time consumption. In consideration of focus speed, DSLR
often obtains a local peak through adopting a fast AF technique,
i.e., a mountain-climbing method. In this case, however, the
autofocus may fail if a near object and a far object co-exist in
the subject frame.
[0007] For instance, FIG. 1 is a schematic diagram illustrating a
focus value curve of an image. Here, the horizontal axis represents
the lens-movement steps, and the vertical axis represents the focus
value. FIG. 2(a) and FIG. 2(b) are schematic diagrams respectively
illustrating a display image on a DSLR while the DSLR is focusing a
scene. The focus value curve C1 shown in FIG. 1 indicates
calculations made on the subject frame as shown in FIG. 2(a), for
instance. According to the subject frame shown in FIG. 2(a), the
to-be-shot object includes a notebook computer, a mouse, and a cup
at a distance, and the focus frame 201 only contains one focus
target (i.e., the notebook computer). As illustrated in FIG. 1, at
the location of the lens corresponding to the lens-movement steps
S1, the local peak F1 may be obtained, i.e., the location of the
lens allows the subject frame to have the optimal sharpness.
However, with reference to FIG. 2(b), after the AF procedure is
successfully performed, another object (a pen) to be shot is also
moved into the focus frame 203 for performing the AF procedure. At
this time, the focus frame 203 contains the relatively far notebook
computer and the relatively near pen. Since the AF procedure is
already successfully performed on the notebook computer, the local
peak may still be searched first from the locations of the lens
corresponding to the lens-movement steps S1 shown by the focus
value curve C1 when the AF procedure is performed once again.
Namely, in the focus frame 203, the DSLR still focuses the
relatively far notebook computer, and thus the autofocus on the
relatively near pen fails. In view of the above, how to develop an
AF method that may achieve favorable efficiency and satisfactory
accuracy is one of the issues to be resolved.
SUMMARY OF THE INVENTION
[0008] The invention is directed to an auto-focus (AF) method that
may switch between different peak focus value searching algorithms
based on the control of an image capturing device by a user, so as
to improve AF accuracy.
[0009] In an embodiment of the invention, an AF method adapted for
an image capturing device is provided. The AF method includes
following steps. It is determined whether a first press signal that
is generated by a user pressing a button of the image capturing
device is detected. If the first press signal is detected, a local
peak searching method is applied to perform an AF procedure.
Besides, it is determined whether a second press signal that is
generated by the user pressing the button is detected. If the
second press signal is not detected, it is determined whether a
first released signal that is generated by the user releasing the
button is detected, and a continuous pressing count is calculated
according to the first released signal and the first press signal
that are continuously generated. Here, the continuous pressing
count is effected by the user continuously pressing and releasing
the button. Whether the continuous pressing count is greater than a
first threshold is determined. If the continuous pressing count is
greater than the first threshold, a global peak searching method is
applied to perform the AF procedure. If the continuous pressing
count is not greater than the first threshold, the local peak
searching method is still applied to perform the AF procedure.
[0010] According to an embodiment of the invention, if the second
press signal is not detected, the step of calculating the
continuous pressing count includes determining whether another
first press signal is detected within a predetermined time period
after detecting the first released signal. If another first press
signal is detected, the continuous pressing count is up counted. If
no other first press signal is detected, an initial value of the
continuous pressing count is configured to be 0.
[0011] According to an embodiment of the invention, the AF method
further includes applying the local peak searching method to
perform the AF procedure and continuously detecting the second
press signal if the continuous pressing count is not greater than
the first threshold.
[0012] According to an embodiment of the invention, the first press
signal is generated by the user pressing the button of the image
capturing device to perform the AF procedure. The second press
signal is generated by the user pressing the button of the image
capturing device to perform an exposure procedure.
[0013] According to an embodiment of the invention, the first press
signal is generated by the user half-pressing the button, and the
second press signal is generated by the user completely pressing
the button.
[0014] In an embodiment of the invention, an AF method adapted for
an image capturing device having a zooming lens is provided. The AF
method includes following steps. It is determined whether a first
press signal that is generated by a user pressing a button of the
image capturing device is detected. If the first press signal is
detected, a local peak searching method is applied to perform an AF
procedure, and a first lens-movement steps corresponding to the
zooming lens is recorded when the AF procedure is successfully
performed. It is determined whether a second press signal that is
generated by the user completely pressing the button is detected.
If the second press signal is not detected, it is determined
whether a first released signal generated by the user releasing the
button is detected, and the continuous pressing count is calculated
according to the first released signal and the first press signal
that are continuously generated. Here, the continuous pressing
count is effected by the user continuously pressing and releasing
the button. Whether the continuous pressing count is greater than a
first threshold is determined. If the continuous pressing count is
greater than the first threshold, a global peak searching method is
applied to perform the AF procedure. If the continuous pressing
count is not greater than the first threshold, the local peak
searching method is applied to perform the AF procedure, and a
second lens-movement steps corresponding to the zooming lens is
recorded when the AF procedure is successfully performed.
[0015] According to an embodiment of the invention, the AF method
further includes following steps. It is determined whether an
absolute value of a difference between the second lens-movement
steps and the first lens-movement steps is less than a step
threshold. If the absolute value of the difference between the
second lens-movement steps and the first lens-movement steps is
less than the step threshold, the step count is up counted. If the
absolute value of the difference between the second lens-movement
steps and the first lens-movement steps is not less than the step
threshold, the continuous pressing count and the step count are
initialized.
[0016] According to an embodiment of the invention, the step of
determining whether the continuous pressing count is greater than
the first threshold further includes determining whether the step
count is greater than a second threshold. If the continuous
pressing count is greater than the first threshold, and the step
count is greater than the second threshold, the global peak
searching method is applied to perform the AF procedure.
[0017] In light of the foregoing, the AF method described herein
may switch between a local peak searching method and a global peak
searching method based on the control of a button of an image
capturing device by a user. Thereby, not only favorable peak
searching speed may be ensured, but also the improvement of AF
accuracy may be guaranteed.
[0018] Several exemplary embodiments accompanied with figures are
described in detail below to further explain the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The accompanying drawings are included to provide further
understanding, and are incorporated in and constitute a part of
this specification. The drawings illustrate exemplary embodiments
and, together with the description, serve to explain the principles
of the invention.
[0020] FIG. 1 is a schematic diagram illustrating a focus value
curve of an image.
[0021] FIG. 2(a) and FIG. 2(b) are schematic diagrams respectively
illustrating a display image on a DSLR while the DSLR is focusing a
scene.
[0022] FIG. 3 is a block diagram illustrating an image capturing
device according to an embodiment of the invention.
[0023] FIG. 4 is a flowchart illustrating an AF method according to
an embodiment of the invention.
[0024] FIG. 5 is a flowchart illustrating an AF method according to
another embodiment of the invention.
[0025] FIG. 6 is a schematic diagram illustrating a focus value
curve of an image according to another embodiment of the
invention.
DETAILED DESCRIPTION OF DISCLOSED EXEMPLARY EMBODIMENTS
[0026] At present, common digital single lens reflex cameras (DSLR)
often have the two-stage press button design (half-press or
full-press). At the first stage, parameters including proper focus,
correct exposure and proper white balance are set; at the second
stage, an exposure procedure is performed, i.e., the photo shoot is
actually taken. Hence, when a user takes a photo with use of the
DSLR having the two-stage press button design, the user may first
half-press the button to activate an auto-focus (AF) function.
Here, the lens of the DSLR performs the AF procedure on the
to-be-shot object in the focus frame. After the user ascertains
that the AF procedure is successfully performed, the user fully
presses the button (the second-stage button) to finish the photo
shoot. According to the AF method described herein, the user may,
based on the control of the button of an image capturing device,
choose to apply different AF searching algorithms. To make the
invention more comprehensible, several embodiments are described
below as examples to prove that the invention can actually be
realized.
[0027] FIG. 3 is a block diagram illustrating an image capturing
device according to an embodiment of the invention. With reference
to FIG. 3, the image capturing device 300 described in the present
embodiment is, for instance, a DSLR, a digital video camcorder
(DVC), and so forth, which should not be construed as a limitation
to the invention. The image capturing device 300 includes an image
sensor 310, a detector 320, an AF module 330, and a processing unit
340. The functions of said components are described below.
[0028] The image sensor 310 includes a photo-sensor 312 and a
zooming lens 314. The photo-sensor 312 is, for instance, a charge
coupled device (CCD), a complementary metal-oxide semiconductor
(CMOS) device, and so on; the image sensor 310 may further include
an aperture, which should not be construed as limitations to the
invention.
[0029] The detector 320 serves to detect an operating signal
generated by the user pressing or releasing a button of the image
capturing device 300.
[0030] The AF module 330 is coupled to the image sensor 310 and may
change the focal distance with use of a step motor that may control
the location of the zooming lens 314. Besides, the AF module 330
may calculate a focus value by applying a local peak searching
method or a global peak searching method.
[0031] The processing unit 340 is, for instance, a central
processing unit (CPU), any other programmable microprocessor or
digital signal processor (DSP) for general or special purposes, and
so on, and the processing unit 340 may serve to control the image
sensor 310, the detector 320, and the AF module 330.
[0032] FIG. 4 is a flowchart illustrating an AF method according to
an embodiment of the invention. The AF method described in the
present embodiment is adapted for the image capturing device 300
depicted in FIG. 3, and the detailed steps of the AF method is
described hereinafter with reference to the descriptions of each
components in the image capturing device 300.
[0033] In the AF method, it is determined whether a first press
signal that is generated by a user pressing a button of the image
capturing device 300 is detected by the detector 320 in a step
S401. Here, the first press signal is generated by the user
pressing the button of the image capturing device 300 to perform
the AF procedure. In the present embodiment, the first press signal
is obtained by the user half-pressing the button of the image
capturing device 300. If the first press signal is detected by the
detector 320, a step S403 may be performed; if not, the detector
320 continues to detect the first press signal.
[0034] In the step S403, the processing unit 340 configures an
initial value of the continuous pressing count to be 0. In a step
S405, the processing unit 340 controls the AF module 330 to perform
the AF procedure through applying the local peak searching method
because the detector 320 detects the first press signal.
[0035] In a step S407, it is determined whether a second press
signal that is generated by the user pressing the button is
detected by the detector 320. Here, the second press signal is
generated by the user pressing the button of the image capturing
device 300 to perform an exposure procedure. In the present
embodiment, the second press signal is obtained by the user
completely pressing the button of the image capturing device 300.
This indicates that the user ascertains that the AF procedure is
successfully performed and determines to take a photo.
[0036] If the detector 320 indeed detects the second press signal,
a step S409 may then be performed, i.e., the processing unit 340
controls the image sensor 310 to take a photo according to a result
of the AF procedure.
[0037] Back to the step S407, if the detector 320 fails to detect
the second press signal, a step S411 may then be performed, i.e.,
the processing unit 340 calculates the continuous pressing count
according to the continuous operating signal generated by the user
continuously releasing and half-pressing the button.
[0038] In a step S413, the processing unit 340 determines whether
the continuous pressing count is greater than a first threshold. If
the continuous pressing count is greater than the first threshold,
the processing unit 340 controls the AF module to perform the AF
procedure through applying a global peak searching method in a step
S415. If not, the AF procedure is still performed through applying
the local peak searching method in a step S417. After that, the
detector 320 continues to detect whether the second press signal is
received in the step S407.
[0039] The step S411 of calculating the continuous pressing count
may be further divided into five sub-steps S4110 to S4118. In the
sub-step S4110, the detector 320 detects whether a first released
signal that is generated by the user releasing the button is
received. If not, go back to the step S407; if yes, the sub-step
S4112 may then be performed, i.e., the image capturing device 300
may display a live view, and thereby the user may either re-adjust
the subject frame after releasing the button or again perform the
AF procedure. The detector 320 then detects whether another first
press signal is received after receiving the first released signal
within a predetermined time period (in the sub-step S4114). Namely,
the processing unit 340 determines whether the difference between
the time of receiving the first released signal and the time of
receiving another first press signal is shorter than a
predetermined time period in the sub-step S4116. If yes, the
processing unit 340 up counts the continuous pressing count in the
sub-step S4118, i.e., the processing unit 340 accumulates 1 to the
continuous pressing count.
[0040] According to inductive experiments, it should be mentioned
that the predetermined time period may be set as 0.5 seconds, and
the first threshold may be set as 5 times, for instance. However,
the invention is not limited thereto, and people having ordinary
skill in the art may determine the predetermined time period and
the first threshold based on actual situations. That is, if another
first press signal is received within 0.5 second after receiving
the first released signal, the continuous pressing count is up
counted by 1. After the continuous pressing count is greater than
5, the global peak searching method is employed to perform the AF
procedure; otherwise, the AF procedure is still performed through
applying the local peak searching method.
[0041] In general, if the user repeatedly half-presses the button
and releases the button within a short period of time, it probably
implies that the image capturing device fails to successfully
perform the AF procedure. Thereby, the user is required to release
the button and then half-press the button again to perform the AF
procedure once more. However, when the local peak searching method
is applied to perform the AF procedure, the autofocus may fail if a
near object and a far object co-exist in the subject frame. At this
time, the global peak searching method may need to be applied to
perform the AF procedure. In the present embodiment, the continuous
pressing count of the user is calculated within a predetermined
time period to determine whether the local peak searching method or
the global peak searching method is applied, so as to improve the
AF accuracy.
[0042] In the event that the user repeatedly half-presses the
button and releases the button within a short period of time, it
may further imply that, in addition to the failure of the image
capturing device to successfully perform the AF procedure, the user
intends to re-select a subject to be shot or adjust the composition
of the subject frame, i.e., rapidly change the scene of
photography. Solutions to the above issue are correspondingly
provided in the following embodiment.
[0043] FIG. 5 is a flowchart illustrating an AF method according to
another embodiment of the invention. The method described in the
present embodiment is also applicable to the image capturing device
300 depicted in FIG. 3. Please refer to FIG. 5.
[0044] It is determined whether a first press signal that is
generated by a user half-pressing a button of an image capturing
device is detected in a step S501. If the first press signal is
detected, initial values of the continuous pressing count and the
step count are configured to be 0 in a step S503. If the first
press signal is not detected, then continue to detect the first
press signal.
[0045] After the continuous pressing count and the step count are
initialized, a local peak searching method is applied to perform an
AF procedure, and a first lens-movement steps corresponding to a
zooming lens is recorded when the AF procedure is successfully
performed (step S505). FIG. 6 is a schematic diagram illustrating a
focus value curve of an image according to another embodiment of
the invention. With reference to FIG. 6, a focus value curve L1
refers to the focus data obtained in the AF procedure, and the
lens-movement steps S1 corresponding to a focus value F1 of a first
region is recorded in the present embodiment.
[0046] In a step S507, it is determined whether a second press
signal that is generated by the user completely pressing the button
is detected. The second press signal, if being detected, indicates
the user ascertains the AF procedure is successfully performed and
decides to take a photo. At this time, the photo may be taken
according to a result of the AF procedure (step S509). If the
second press signal is not detected, a continuous operating signal
generated by the user continuously releasing and half-pressing the
button is detected, so as to calculate the continuous pressing
count (step S511). Here, the continuous operating signal refers to
the first press signal and the first released signal that are
continuously generated. The step S511 may be further divided into
five sub-steps S5110 to S5118 which are identical or similar to the
sub-steps S4110 to S4118 described in the previous embodiment.
Therefore, relevant descriptions are omitted hereinafter.
[0047] It is then determined whether the continuous pressing count
is greater than a first threshold and whether the step count is
greater than a second threshold (step S513). If the continuous
pressing count is greater than the first threshold, and the step
count is greater than the second threshold, a global peak searching
method is applied to perform the AF procedure in a step S515;
otherwise, the local peak searching method is applied to perform
the AF procedure again, and a second lens-movement steps
corresponding to the zooming lens is recorded when the AF procedure
is successfully performed (step S517). With reference to FIG. 6, a
focus value curve L2 refers to the focus data obtained in this AF
procedure, and the lens-movement steps S2 corresponding to a focus
value F2 of a second region is recorded in this step.
[0048] Different from the previous embodiment, the present
embodiment discloses the AF method that further includes
determining whether an absolute value of a difference between the
lens-movement steps S2 (i.e., the second lens-movement steps) and
the lens-movement steps S1 (i.e., the first lens-movement steps) is
less than a step threshold (step S519). If the absolute value of
the difference between the lens-movement steps S2 and the
lens-movement steps S1 is less than the step threshold, the step
count is up counted, i.e., 1 is accumulated to the step count;
otherwise, the continuous pressing count and the step count are
initialized, i.e., the initial values of the continuous pressing
count and the step count are again configured to be 0 in the step
S503.
[0049] In the present embodiment, the predetermined time period may
be set as 0.5 seconds, and the first threshold may be set as 5
times, for instance. Besides, according to inductive experiments,
the second threshold may be set as 2 times, and the step count may
be set as 100 steps, for instance. The above-mentioned parameters
are preferable but should not be construed as limitations to the
invention. People having ordinary skill in the art may determine
the parameters based on actual situations.
[0050] In the present embodiment, the first local peak searching
method is applied to perform the AF procedure, and the
lens-movement steps S1 corresponding to the zooming lens is
recorded when the AF procedure is successfully performed; the
second local peak searching method is applied to perform another AF
procedure, and the lens-movement steps S2 corresponding to the
zooming lens is recorded when the AF procedure is successfully
performed. The lens-movement steps S2 is compared with the
lens-movement steps S1, and if the difference there-between is
greater than 100 steps, it is determined that the user already
changes the scene of photography rapidly, i.e., the variation in
the photo of the to-be-shot subject is overly significant. In this
case, the local peak search method is still suitable for performing
the fast AF procedure. By contrast, if the user quickly
half-presses the button and releases the button repeatedly to focus
the same scene (i.e., to take the photo of the same to-be-shot
subject), the global peak searching method is applied to perform
the AF procedure. Thereby, as described in the related art, under
the same scene of photography, the focus procedure is first
performed on the relatively far object; after a relatively near
object appears in the focus frame, the global peak searching method
may be automatically applied to perform the AF procedure, so as to
prevent the failure to focus the relatively near object.
[0051] To sum up, based on the control of a button of an image
capturing device by a user, the local peak searching method or the
global peak searching method may be automatically applied. In
addition, when the AF procedure is successfully performed, the
resultant number of the lens-movement steps may help determine
whether the user rapidly changes the scene of photography. A
different focus value searching algorithm may be applied only when
the user is determined to quickly half-press and release the button
of the image capturing device repeatedly to focus the same scene.
Thereby, not only favorable peak searching speed may be ensured,
but also the improvement of AF accuracy may be guaranteed.
[0052] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
invention cover modifications and variations of this invention
provided they fall within the scope of the following claims and
their equivalents.
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